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During the evolution of SARS-CoV-2 in humans, a D614G substitution in the spike glycoprotein (S) has emerged; virus containing this substitution has become the predominant circulating variant in the COVID-19 pandemic1. However, whether the increasing prevalence of this variant reflects a fitness advantage that improves replication and/or transmission in humans or is merely due to founder effects remains unknown. Here we use isogenic SARS-CoV-2 variants to demonstrate that the variant that contains S(D614G) has enhanced binding to the human cell-surface receptor angiotensin-converting enzyme 2 (ACE2), increased replication in primary human bronchial and nasal airway epithelial cultures as well as in a human ACE2 knock-in mouse model, and markedly increased replication and transmissibility in hamster and ferret models of SARS-CoV-2 infection. Our data show that the D614G substitution in S results in subtle increases in binding and replication in vitro, and provides a real competitive advantage in vivo—particularly during the transmission bottleneck. Our data therefore provide an explanation for the global predominance of the variant that contains S(D614G) among the SARS-CoV-2 viruses that are currently circulating.

Ralstonia eutrophaH16 is a denitrifying microorganism able to use nitrate and nitrite as terminal electron acceptors under oxygen deprivation. To identify proteins showing an altered expression pattern in response to oxygen supply, R. eutrophacells grown aerobically and anaerobically were compared in a comprehensive proteome and transcriptome approach. Nearly 700 proteins involved in several processes including respiration, formation of cell appendages, and DNA and cofactor biosynthesis were found to be differentially expressed. A combination of 1D gel-LC and conventional 2D gel analysis of six consecutive sample points covering the entire denitrification sequence revealed a detailed view on the shifting abundance of the key proteins of denitrification. Denitrification- or anaerobiosis-induced alterations of the respiratory chain included a distinct expression pattern for multiple terminal oxidases. Alterations in the central carbon metabolism were restricted to a few key functions including the isoenzymes for aconitase and isocitrate dehydrogenase. Although R. eutrophais a strictly respiratory bacterium, the abundance of certain fermentation enzymes was increased. This work represents a comprehensive survey of denitrification on the proteomic and transcriptomic levels and provides unique insight into how R. eutrophaadapts its metabolism to low oxygen conditions.

Hydrogenovibrio marinus was suggested to have only membrane-bound hydrogenase (MBH). The change of cultivation pO2did not affect the molecular species of hydrogenase expressed. We propose the MBH is grouped in class I [NiFe] MBH according to the subunit composition, size (Mw 38,000 and Mw 74,000 subunits) and N-terminal sequences of the subunits, and arrangement of the structural genes. Ni-requirement for the autotrophic growth on H2also suggested the MBH is the Ni-containing type. Southern hybridization analysis using a part of the MBH gene showed a possibility of the presence of two highly homologous MBHs which were not separated by SDS-PAGE.

Nitric oxide (NO) reductase was purified from Ralstonia eutropha(formerly Alcaligenes eutrophus) using a two step chromatographic procedure. Unlike the common NO reductases, the enzyme consists of a single subunit of 75 kDa which contains both high‐spin and low‐spin heme b, but lacks heme c. One additional iron atom, probably a ferric non‐heme iron, was identified per enzyme molecule. Whereas reduced cytochrome cwas ineffective as electron donor, NO was reduced at a specific activity of 2.3 μmol/min per mg of protein in the presence of 2‐methyl‐1,4‐naphthoquinol.

Abstract: Alcaligenes eutrophus H16 harbors seven hyp genes (hypA, B, F, C, D, E, and X) as part of the hydrogenase gene cluster on megaplasmid pHG1. Here we demonstrate that three of the hyp genes (hypA, B, and F) are duplicated in A. eutrophus, which explains the lack of a phenotypic change in single-site mutants impaired in one of the two copies. Mutants with lesions in both copies showed clear alterations in hydrogenase activities. Deletions in hypF1 and hypF2 completely abolished activities of the soluble hydrogenase and of the membrane-bound hydrogenase, mutations in hypA1 and hypA2 totally blocked the membrane-bound hydrogenase activity, while residual soluble hydrogenase activity accounted for the extremely slow growth of the strain on H2. Both hydrogenase activities of mutants defective in hypB1 and hypB2 were partially restored by elevating the concentration of nickel chloride in the medium. Reduction of hydrogenase activities in the double mutants correlated with varying degrees of maturation deficiency based upon the amount of unprocessed nickel-free hydrogenase precursor. Despite a high identity between the two copies of hyp gene products, substantial structural differences were identified between the two copies of hypF genes. HypF1, although functionally active, is a truncated version of HypF2, whose structure resembles HypF proteins of other organisms. Interestingly, the N-terminus of HypF2, which is missing in the HypF1 counterpart, contains a putative acylphosphatase domain in addition to a potential metal binding site.

Quality management and independent assessment of high-throughput sequencing-based virus diagnostics have not yet been established as a mandatory approach for ensuring comparable results. The sensitivity and specificity of viral high-throughput sequence data analysis are highly affected by bioinformatics processing using publicly available and custom tools and databases and thus differ widely between individuals and institutions.